The embodiments of the invention discussed herein relate to systems and methods for measuring and controlling ultrasound in a vessel.
The present invention relates to ultrasonic cleaning and ultrasonic processing systems, and more particularly, to systems, probes, ultrasonic generators (referred to herein as ultrasonic transmitters to distinguish them from ultrasonic receivers), ultrasonic transducers, circuitry and methods that clean and/or process by coupling ultrasonic waves into a liquid. Prior art ultrasonic systems lack the ability to measure and control the ultrasound in a vessel to a predetermined value of ultrasonic activity, which is related to the total acoustic energy in the vessel. This invention improves the performance of an ultrasonic system by introducing consistency of process either through measurement of the process and/or control of the process based on the measured ultrasonic activity.
The prior art describes probes that measure ultrasonic waves, cavitation intensity and other ultrasonic characteristics at a certain location in an ultrasonic vessel. This is most useful for ultrasonic vessels with uniform ultrasonic fields because the point measurement can be used as a measure of the ultrasonic characteristics in the rest of the vessel, however, in a practical situation where the vessel is loaded with parts to be cleaned, the ultrasonic field is seldom uniform.
Examples of prior art probes are shown in U.S. Pat. Nos. 5,931,173; 6,288,476 B1 and 6,450,184 B1. Each of these probes measure the ultrasonic characteristics at the place in the vessel where the probe is located. Because of the non uniform ultrasonic field in a practical ultrasonic vessel containing parts to be cleaned or processed, this point measurement often does not give accurate information about the over all ultrasonic field in the vessel.
Therefore, there is a need in the field of ultrasonic processing and ultrasonic measurement to measure a characteristic that is representative of the total ultrasonic activity within a vessel and use this measurement to control the process.
The embodiments of the present invention relate to the applied uses of ultrasonic energy, and in particular the application and control of ultrasonic energy to clean and process parts within a liquid. Generally, an ultrasonic transmitter drives one or more ultrasonic transducers, or arrays of transducers, coupled to a liquid to clean and/or process a part. In the embodiments disclosed herein, the liquid is held within a vessel; and the transducers mount on or within the vessel to impart ultrasound into the liquid.
When the transmitted signal from the ultrasonic transmitters undergoes a power change (for example, is changed from supplying power to an OFF condition), measurement of the ultrasonic initial amplitude and decay time in the vessel is then received and monitored by the transducers. The ultrasonic initial amplitude and decay time is a measure that can be related to the ultrasonic activity in the vessel prior to the power change. The resulting signal is sent to the ultrasonic receiver, which can record the magnitude and shape of the changes in the ultrasonic signal over time following the power change. A function of the initial amplitude and decay time can then be displayed to show the ultrasonic activity of the system. In this way, measurement of ultrasonic activity in a vessel can be made at any time, or at various intervals, by inserting a power change. Information regarding the ultrasonic activity in the vessel can be displayed for use by an operator of the equipment or fed back to the transmitter for automatic adjustment of the process.
The preceding embodiments of the invention disclose using the same transducer(s) for producing and transmitting an ultrasonic signal, as well as for receiving and measuring the ultrasonic signal over time after the power change. Another embodiment of the invention uses an additional transducer, which can either be a probe or a different transducer used as a probe, to receive the ultrasonic characteristics during and/or after a power change from the transmitting transducers. The typical probe would be made by mounting piezoelectric ceramic in a housing, as is common in the art. The unique feature of this probe, or separate transducer functioning as a probe, is that it works in conjunction with the transmitting transducers and measures the magnitude and shape of the ultrasonic changes over time during and/or after a power change in the transmitted ultrasonic signal.
In still another embodiment of the invention, the steady state magnitude of the ultrasonic signal measured by the probe, or separate transducer functioning as a probe, is recorded as a function of frequency (for example, by a spectrum analyzer). This provides information regarding the magnitude of the ultrasonic signal, as well as frequency components that are useful in determining the size of cavitation implosions within the liquid-containing vessel.
Moreover, one of ordinary skill in the art will readily appreciate that a common way to introduce an ultrasonic signal into a liquid-containing vessel is by use of an xe2x80x9cimmersible.xe2x80x9d An immersible, as used herein, is defined as a sealed container that holds one or more transducers and that is immersed in the vessel. The teachings of this invention are applicable to both vessel-mounted transducers and immersible mounted transducers and an immersible that forms a self-contained measuring system.